Iron club head and iron-headed golf club

ABSTRACT

The present invention relates to an iron club head for an iron golf club. The iron club head  1  includes a front area  2  having a front wall for defining a striking face, and a rear area  3  connected to the front area  2 . The rear area  3  is formed from at least a sole portion  32 , a toe portion  33  and a top blade portion  34 . The front area has a rib  23  extending from the outer peripheral edge of the front wall toward the rear area at portions thereof corresponding to at least the sole portion, the toe portion and the top blade portion of the rear area. The rear area is joined to the front area at the end surface of the rib.

FIELD OF THE INVENTION

[0001] The present invention relates to iron golf club heads. Moreparticularly, the present invention relates to an iron club head thathas high strength and a wide sweet area, and that makes it easy to hit agolf ball and send it high into the air. The present invention alsorelates to an iron golf club using such an iron golf club head.

DESCRIPTION OF THE RELATED ART

[0002] Club heads for iron golf clubs include cavity type iron clubheads in which a face part for defining a striking face and a sole partfor defining a sole surface are integrally formed with each other andwhich has a recess or cavity opening in the back thereof, as a headstructure having a lowered center of gravity to make it easy to hit agolf ball and send it high into the air. Among cavity type iron clubheads is one type which has a head structure in which a front part fordefining a striking face and a rear part for defining a sole surface,which are produced separately from each other, are joined to each other.On the other hand in club heads for wood golf clubs, hollow type clubheads are the mainstream, wherein a face part and a sole part, which areformed separately from each other, are joined together into a club headwith a hollow inside.

[0003] Iron golf clubs are required to provide high strength and a widesweet area. However, the conventional joined type iron club head has astructure as shown in FIG. 1, in which a flat plate-shaped front part aand a rear part b having a sole portion are joined directly to eachother. Therefore, one problem which often occurs with the conventionaljoined type iron club head is that it is difficult to ensure that it hassufficiently high strength and it is impossible to widen the sweet area.

[0004] Iron golf clubs are required to perform in such a way that makesit easy to hit a golf ball and send it high into the air. For the latterrequirements, deepening and lowering the center of gravity of the ironclub head is extremely effective. If the center of gravity of the ironclub head is deepened, the loft angle of the club head when impacting agolf ball increases. If the center of gravity of the iron club head islowered, it is likely that a ball will be struck at a point near thecenter of gravity of the club head. In either case, it becomes easy tohit a golf ball and send it high into the air.

[0005] In this regard, the conventional integral cavity type iron clubhead is disadvantageous as follows. It is theoretically possible todeepen and lower the center of gravity of the iron club head by addingan extra weight thereto, for example, by fitting an insert into the solesurface. However, this causes the head to increase in weight.Consequently, the overall weight of the golf club and consequently theswing weight increase. Thus, addition of an extra weight exerts aninfluence upon the swing. Conversely, if the weight of the face part andits peripheral portion is reduced to decrease the overall weight of theclub head, rigidity is reduced, resulting in an increase in distortionof the clubface. Accordingly, the iron club head becomes unfit for use.

[0006] Regarding hollow type club heads for wood golf clubs, club headsemploying a cup-face design in which a rib is formed along theperipheral edge of the face part, and the face part is joined to thesole part at the rib are already available. However, the application ofthe cup-face type face part to wood club heads is aimed mainly atincreasing the strength at the joint between the sole part and the facepart and/or its vicinities. Moreover, in conventional cavity type woodclub heads, the face part and the sole part are generally made of thesame material.

[0007] Under these circumstances, the present inventors conductedexhaustive studies to overcome the above-described problems and toattain a structure that enables the sweet area to be widened whilemeeting the requirements of iron club heads, i.e. the requirements forrigidity of the club head body and the strength against an impactapplied to the club head when striking a golf ball. As a result, it wasfound that it is possible, by radically modifying the club headstructure, to widen the sweet area while meeting the requirements forthe overall rigidity of the club head and the strength against an impactapplied to the club head when striking a golf ball, and accomplished thepresent invention on the basis of this finding.

SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide an iron clubhead with excellent strength and a wide sweet area by modifying thestructure of the front area so that there is a front wall for defining astriking face and the structure of a rear area is joined to the frontarea.

[0009] Another object of the present invention is to provide an ironclub head with a deepened and lowered center of gravity by making thefront area material have a smaller specific gravity than that of thematerial of the rear area.

[0010] A further object of the present invention is to provide an irongolf club having an iron club head with the above-described structure.

[0011] The present invention provides an iron club head for an iron golfclub. The iron club head includes a front area with a front wall fordefining a striking face, and a rear area connected to the front area.The rear area is formed from at least a sole portion, a toe portion anda top blade portion. The front area has a rib extending from the outerperipheral edge of the front wall toward the rear area at portionsthereof corresponding to at least the sole portion, the toe portion andthe top blade portion of the rear area. The rear area is joined to thefront area at the end surface of the rib.

[0012] According to the present invention, it is possible to increasethe overall rigidity of the club head and to improve strength againstthe impact applied to the club head when striking a golf ball. Inaddition, the sweet area can be widened.

[0013] In the above-described iron club head, the front area may be madeof a material with a smaller specific gravity than that of the materialof the rear area. Thus, the center of gravity can be deepened andlowered.

[0014] The material for the front area and the material for the reararea may be adopted on the basis of the strength, specific gravity, etc.thereof. For example, the material of the front area may be titanium ora titanium alloy, and the material of the rear area may be a stainlesssteel. The specific gravity of titanium is 4 to 5 g/cm³. The specificgravity of the stainless steel is 7 to 10 g/cm³.

[0015] Further, the sole portion of the rear area may be weighted todeepen and lower the center of gravity. For example, an insert made of amaterial having a larger specific gravity than that of the material ofthe rear area may be joined to the sole portion.

[0016] Another application of this invention is to provide an iron golfclub which has an iron club head. The iron club head includes a frontarea with a front wall for defining a striking face, and a rear areaconnected to the front area. The rear area is formed from at least asole portion, a toe portion and a top blade portion. The front area hasa rib extending from the outer peripheral edge of the front wall towardthe rear area at portions thereof corresponding to at least the soleportion, the toe portion and the top blade portion of the rear area. Therear area is joined to the front area at the end surface of the rib.

[0017] Thus, it is possible to increase the overall rigidity of the clubhead of the iron golf club and to improve the strength against theimpact applied to the club head when striking a golf ball. In addition,the sweet area can be widened.

[0018] In the above-described golf club, the front area of the club headmay be made of a material with a smaller specific gravity than that ofthe material of the rear area. Thus, the center of gravity can bedeepened and lowered.

[0019] The material for the front area and the material for the reararea may be adopted on the basis of strength, specific gravity, etc.thereof. For example, the material of the front area may be titanium ora titanium alloy, and the material of the rear area may be a stainlesssteel. The specific gravity of titanium is 4 to 5 g/cm³. The specificgravity of the stainless steel is 7 to 10 g/cm³.

[0020] Further, the sole portion of the rear area may be weighted todeepen and lower the center of gravity. For example, an insert made of amaterial having a larger specific gravity than that of the material ofthe rear area may be joined to the sole portion. It should be noted thatthe iron club head and a club shaft may be connected through a hoselinserted into the neck portion, for example. The hosel may be formed asa part separate from the iron club head from a material with a smallerspecific gravity than that of the material of the rear area of the ironclub head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a sectional view of a conventional joined type iron clubhead.

[0022]FIG. 2 is a front view of one embodiment of the iron club headaccording to the present invention.

[0023]FIG. 3 is a side view of the iron club head shown in FIG. 2.

[0024]FIG. 4 is a sectional view of the iron club head shown in FIG. 2as seen along the arrow A-A.

[0025]FIG. 5 is a sectional view of the iron club head shown in FIG. 2as seen along the arrow B-B.

[0026]FIG. 6 is a sectional view as seen along the arrow D-D in FIG. 3,showing a hosel mounting portion of the iron club head in FIGS. 2 and 3and a hosel secured to the hosel mounting portion.

[0027]FIG. 7 is a sectional view similar to FIG. 4, showing anotherembodiment of the iron club head according to the present invention.

[0028]FIG. 8 is a graph showing the results of a test for measuring thecoefficient of restitution of a conventional club head and a club headaccording to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Embodiments of the iron club head according to the presentinvention will now be described below with reference to the accompanyingdrawings.

[0030] FIGS. 2 to 5 show an iron club head 1 as one embodiment of thepresent invention. The iron club head 1 has a front area 2 for defininga striking face and a rear area 3. The front area 2 and the rear area 3are joined together into an integral iron club head. The front area 2has a front wall 22 for defining a striking face 21 and a rib 23extending from the peripheral portion of the front wall 22 rearward(toward the rear area). The front wall 22 and the rib 23 are formed inan integral structure. In this embodiment, the rib 23 is not formed overthe entire perimeter of the front wall 22. That is, the rib 23 is formedon the sole side, toe side and top blade side of the iron club head butnot on the heel side thereof. A rear area-side end surface (left endsurface in FIG. 4) 26 of the rib 23 forms a joint surface for connectionwith the rear area 3. Another joint surface 27 for connection with therear area 3 is formed at the hosel mounting side of the front area. Thestriking face 21 is formed with a plurality of scorelines 24 extendinghorizontally (laterally in FIG. 2). In this embodiment, the front partis made of titanium or a titanium alloy, but it may be made of analuminum alloy or a magnesium alloy. It should be noted that the frontwall for forming the striking face need not always have a uniformthickness over the entire area thereof but may be formed to be thick atthe center and thin at the peripheral portion thereof to improve thespring characteristics of the clubface while maintaining the requiredstrength. In this case, the back of the striking face may be convexlycurved, by way of example. Alternatively, the thickness of the frontwall may be changed stepwisely or continuously so that the center of thefront wall is thickest.

[0031] The rear area 3 has a sole portion 32 for defining a sole of theiron club head, a toe portion 33 for defining a toe, a top blade portion34 for defining a top blade, and a hosel mounting portion 35. Theseportions are integrally formed with each other. In this embodiment, theabove-described portions of the rear area 3 are integrally made of astainless steel material. Respective end surfaces 36 of the sole portion32, the toe portion 33 and the top blade portion 34, which are closer tothe front area 2, are in the same plane and constitute a joint surfacefor connection with the front area 2. Another joint surface 37 forconnection with the front area 2 is formed on the side of the rear area3 closer to the hosel mounting portion 35. The front area 2 and the reararea 3 are joined together at the end surfaces 26 and 36 and the jointsurfaces 27 and 37 by a publicly known joining method and are thusformed into an integral structure. Accordingly, the iron club head 1 hasa cavity C defined by the front wall, the rear wall, the sole portion,the top blade portion, the toe portion, etc.

[0032] Thus, no part of the sole portion is formed in the front area 2of the iron club head 1. Therefore, it is possible to reduce the amountof material used to form the front area. Accordingly, it is possible tosave on material costs even in the case where the front area is made ofa costly material having high impact strength, such as titanium or atitanium alloy. Further, it is possible to deepen and lower the centerof gravity of the iron club head by forming the rear area from amaterial having a larger specific gravity than that of the material ofthe front area, such as a stainless steel material. Further, because therib is substantially formed over the entire perimeter of the front area,strength can be increased, and the clubface area can be widened. Thus,it is possible to minimize distortion of the striking face which occurswhen striking a golf ball.

[0033] The hosel mounting portion 35 has, as shown in FIG. 6, a steppedhole 38 with a circular cross-sectional configuration. The distal end 41(lower end in FIG. 6) of a hosel 4 is inserted in the stepped hole 38.In this embodiment, the rear area 3 and the hosel 4 are joined togetherby combining thread engagement and welding to increase the jointstrength. However, the rear area 3 and the hosel 4 may be joinedtogether by a publicly known joining method. The hosel 4 is formed in atubular shape as a whole from a material having a smaller specificgravity than that of the material of the rear area 3, such as titaniumor a titanium alloy. The hosel 4 has an axial hole 42. The lower end ofa golf clubshaft 5 is fitted and secured in the axial hole 42. Becausethe hosel 4 is formed as a member separate from the rear area by using amaterial with a smaller specific gravity than that of the material ofthe rear area, it is possible to lower the center of gravity of the headpart of the iron golf club.

[0034] It should be noted that in the foregoing embodiment the jointsurfaces 26 and 27 of the front area and hence the joint surfaces 36 and37 of the rear area are joined to the mating joint surfaces atrespective plane surfaces as illustrated in the figures. To increase thejoint strength, however, the arrangement may be as follows. A projectionis formed on the rib of the front area, and a recess fittable with theprojection is formed in a corresponding portion of the rear area, oralternatively, a recess is formed in the rib of the front area, and aprojection fittable in the recess is formed on a corresponding portionof the rear area, and the projection and the recess are fitted to eachother to join the front area and the rear area together. Further, therib may be formed also on the heel mounting side of the front area tomake the joint surfaces flush with each other.

[0035]FIG. 7 shows a modification 1 a of the iron club head according tothe present invention. The iron club head 1 a also comprises a frontarea 2 for defining a striking face 21 a, and a rear area 3 joined tothe front area 2. The iron club head 1 a in this embodiment differs fromthe above-described embodiment only in the structure of the rear area 3a. Therefore, only the part in which the iron club head 1 a differs fromthe foregoing embodiment will be described below, and a description ofthe rest of the iron club head 1 a is omitted.

[0036] The rear area 3 a has a cut portion 311 a formed in the lowercorner edge (in FIG. 7) of the sole portion 32 a. An insert 6 is fittedinto and joined to the cut portion 311 a. The insert 6 has the sameconfiguration as that of the cut portion and is made of a material witha larger specific gravity than that of the material of the rear area(specific gravity: approximately from 10 to 20 g/cm³), e.g. tungsten.With this arrangement, the specific gravity of the material forming thesole portion of the iron club head increases, and the center of gravityof the iron club head shifts rearward in relation to the mountingposition of the insert 6. Accordingly, it is possible to further deepenand lower the center of gravity of the iron club head.

[0037] The following is a description of the results of a test carriedout to compare the conventional cavity type iron club head shown in FIG.1 [hereinafter referred to as “the conventional club head” (Model:MACTEC NV No. 5 Iron)] with the cavity type iron club head according toone embodiment of the present invention [hereinafter referred to as “theclub head of the present invention” (Model: MACTEC NV2 No. 5 Iron) interms of the coefficient of restitution (COR) and the extent of thesweet area.

[0038] The test was performed 10 times for each of the conventional clubhead and the club head of the present invention at each of three points:the sweet spot, that is, the center of gravity (SS); a point (P_(TOE))10 mm away from the sweet spot toward the toe portion (TOE); and a point(P_(HEEL)) 10 mm away from the sweet spot toward the heel portion(HEEL). The conventional club head (club head A), had a front area madeof titanium and a rear area made of a stainless steel. The overallweight was 255.4 g. Regarding the conventional club head, measuredvalues in the test carried out 10 times for each of the above-describedthree points are as shown in Table 1 below. The club head of the presentinvention (club head B) also had a front area made of titanium and arear area made of a stainless steel. The overall weight was 257.8 g.Regarding the club head of the present invention, measured values in thetest carried out 10 times for each of the above-described three pointsare as shown in Table 2 below. TABLE 1 Conventional club head A Test No.SS P_(HEEL) P_(TOE) 1 0.775 0.746 0.749 2 0.773 0.744 0.747 3 0.7710.741 0.744 4 0.758 0.736 0.739 5 0.757 0.734 0.738 6 0.756 0.732 0.7357 0.754 0.730 0.734 8 0.754 0.728 0.732 9 0.751 0.725 0.730 10  0.7510.724 0.730 Total COR 7.600 7.340 7.378 Average COR 0.760 0.734 0.738

[0039] TABLE 2 Club head of the present invention B Test No. SS P_(HEEL)P_(TOE) 1 0.814 0.799 0.802 2 0.814 0.799 0.801 3 0.813 0.797 0.799 40.811 0.797 0.799 5 0.809 0.795 0.797 6 0.808 0.795 0.797 7 0.808 0.7930.795 8 0.805 0.791 0.794 9 0.805 0.791 0.792 10  0.804 0.789 0.792Total COR 8.091 7.946 7.968 Average COR 0.809 0.795 0.797

[0040] Average values of the measured values at each of theabove-described three points obtained as the result of the test carriedout 10 times for each of the above club heads are as shown in Table 3below: TABLE 3 Type Position Weight (g) COR Club head A SS 255.4 0.760P_(HEEL) 255.4 0.734 P_(TOE) 255.4 0.738 Club head B SS 257.8 0.809P_(HEEL) 257.8 0.795 P_(TOE) 257.8 0.797

[0041]FIG. 8 is a graph which shows the results of the test by using thevalues shown in Table 3 to facilitate better understanding. It can beseen from the graph that the club head of the present invention exhibitsa high coefficient of restitution as a whole in comparison to theconventional club head and is capable of sending the ball further thanwith the conventional club head. It can also be seen that the rate atwhich the value of the coefficient of restitution decreases at the pointP_(TOE) and the point P_(HEEL) with respect to the coefficient ofrestitution at the sweet spot SS is lower in the club head of thepresent invention than in the conventional club head. This shows thatthe sweet area of the club head of the present invention is wider thanthat of the conventional club head.

[0042] The Present Invention Offers the Following Advantageous Effects

[0043] (a) The front area of the iron club head has a rib extending fromthe outer peripheral edge of the front wall toward the rear area at atleast the sole portion, the toe portion and the top blade portion, andthe rear area is joined to the front area at the end surface of the rib.Accordingly, it is possible to relieve the impact acting on the endsurface of the striking face and to prevent breakage. Further, it isclear from the results shown in FIG. 8 that the sweet area can bewidened.

[0044] (b) The coefficient of restitution of the striking face can beincreased in comparison to the conventional structure.

[0045] (c) The center of gravity of the iron club head can be deepenedand lowered by making the rear area of a material having a largerspecific gravity than that of the material of the front area.

[0046] (d) Because the iron club head comprises the front area and therear area and the volumetric capacity of the front area for defining thestriking face is reduced, it is possible to save the material cost evenin the case where the front area is made of a costly material which hashigh impact strength, such as titanium or a titanium alloy.

[0047] (e) The center of gravity of the iron club head can be furtherdeepened and lowered by securing an insert in the sole portion of therear area, said insert being made of a material having a larger specificgravity than that of the material of the rear area.

[0048] (f) By making the hosel of a material have a smaller specificgravity than that of the material of the rear area of the iron clubhead, the center of gravity of the head part of the iron golf club canbe lowered further than that of the head part of a golf club using onlythe above-described iron club head.

1. An iron club head for an iron golf club, comprising: a front areahaving a front wall for defining a striking face; and a rear areaconnected to said front area; wherein said rear area is formed from atleast a sole portion, a toe portion and a top blade portion; and saidfront area has a rib extending from the outer peripheral edge of saidfront wall toward said rear area at portions thereof corresponding to atleast said sole portion, toe portion and top blade portion of said reararea, said rear area being joined to said front area at an end surfaceof said rib.
 2. An iron club head according to claim 1, wherein saidfront area is made of a material having a smaller specific gravity thanthat of a material of said rear area.
 3. An iron club head according toclaim 1, wherein a material of said front area is titanium or a titaniumalloy, and a material of said rear area is a stainless steel.
 4. An ironclub head according to claim 1, wherein an insert made of a materialhaving a larger specific gravity than that of a material of said reararea is joined to the sole portion of said rear area.
 5. An iron golfclub having an iron club head, said iron club head including: a frontarea having a front wall for defining a striking face; and a rear areaconnected to said front area; wherein said rear area is formed from atleast a sole portion, a toe portion and a top blade portion; and saidfront area has a rib extending from the outer peripheral edge of saidfront wall toward said rear area at portions thereof corresponding to atleast said sole portion, toe portion and top blade portion of said reararea, said rear area being joined to said front area at an end surfaceof said rib.
 6. An iron golf club according to claim 5, wherein saidfront area is made of a material having a smaller specific gravity thanthat of a material of said rear area.
 7. An iron golf club according toclaim 5, wherein the material of the front area of said iron club headis titanium or a titanium alloy, and the material of the rear area ofsaid iron club head is a stainless steel.
 8. An iron golf club accordingto claim 5 wherein an insert made of a material having a larger specificgravity than that of the material of the rear area of said iron clubhead is joined to the sole portion of said rear area.
 9. An iron golfclub according to claim 5, wherein a hosel for connecting together saidiron club head and a clubshaft is formed as a member separate from saidiron club head from a material having a smaller specific gravity thanthat of the material of the rear area of said iron club head.
 10. Aniron club head according to claim 2, wherein a material of said frontarea is titanium or a titanium alloy, and a material of said rear areais a stainless steel.
 11. An iron club head according to claim 2,wherein an insert made of a material having a larger specific gravitythan that of a material of said rear area is joined to the sole portionof said rear area.
 12. An iron club head according to claim 3, whereinan insert made of a material having a larger specific gravity than thatof a material of said rear area is joined to the sole portion of saidrear area.
 13. An iron club head according to claim 10, wherein aninsert made of a material having a larger specific gravity than that ofa material of said rear area is joined to the sole portion of said reararea.
 14. An iron golf club according to claim 6, wherein the materialof the front area of said iron club head is titanium or a titaniumalloy, and the material of the rear area of said iron club head is astainless steel.
 15. An iron golf club according to claim 6, wherein aninsert made of a material having a larger specific gravity than that ofthe material of the rear area of said iron club head is joined to thesole portion of said rear area.
 16. An iron golf club according to claim7, wherein an insert made of a material having a larger specific gravitythan that of the material of the rear area of said iron club head isjoined to the sole portion of said rear area.
 17. An iron golf clubaccording to claim 14, wherein an insert made of a material having alarger specific gravity than that of the material of the rear area ofsaid iron club head is joined to the sole portion of said rear area. 18.An iron golf club according to claim 6, wherein a hosel for connectingtogether said iron club head and a clubshaft is formed as a memberseparate from said iron club head from a material having a smallerspecific gravity than that of the material of the rear area of said ironclub head.
 19. An iron golf club according to claim 7, wherein a hoselfor connecting together said iron club head and a clubshaft is formed asa member separate from said iron club head from a material having asmaller specific gravity than that of the material of the rear area ofsaid iron club head.
 20. An iron golf club according to claim 14,wherein a hosel for connecting together said iron club head and aclubshaft is formed as a member separate from said iron club head from amaterial having a smaller specific gravity than that of the material ofthe rear area of said iron club head.